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1 /* |
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2 * Copyright 1996-2005 Sun Microsystems, Inc. All Rights Reserved. |
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
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4 * |
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5 * This code is free software; you can redistribute it and/or modify it |
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6 * under the terms of the GNU General Public License version 2 only, as |
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7 * published by the Free Software Foundation. Sun designates this |
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8 * particular file as subject to the "Classpath" exception as provided |
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9 * by Sun in the LICENSE file that accompanied this code. |
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10 * |
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11 * This code is distributed in the hope that it will be useful, but WITHOUT |
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12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
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13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
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14 * version 2 for more details (a copy is included in the LICENSE file that |
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15 * accompanied this code). |
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16 * |
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17 * You should have received a copy of the GNU General Public License version |
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18 * 2 along with this work; if not, write to the Free Software Foundation, |
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19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
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20 * |
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21 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, |
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22 * CA 95054 USA or visit www.sun.com if you need additional information or |
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23 * have any questions. |
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24 */ |
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25 |
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26 package java.util.zip; |
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27 |
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28 /** |
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29 * A class that can be used to compute the Adler-32 checksum of a data |
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30 * stream. An Adler-32 checksum is almost as reliable as a CRC-32 but |
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31 * can be computed much faster. |
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32 * |
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33 * @see Checksum |
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34 * @author David Connelly |
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35 */ |
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36 public |
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37 class Adler32 implements Checksum { |
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38 private int adler = 1; |
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39 |
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40 /** |
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41 * Creates a new Adler32 object. |
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42 */ |
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43 public Adler32() { |
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44 } |
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45 |
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46 |
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47 /** |
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48 * Updates checksum with specified byte. |
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49 * |
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50 * @param b an array of bytes |
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51 */ |
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52 public void update(int b) { |
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53 adler = update(adler, b); |
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54 } |
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55 |
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56 /** |
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57 * Updates checksum with specified array of bytes. |
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58 */ |
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59 public void update(byte[] b, int off, int len) { |
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60 if (b == null) { |
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61 throw new NullPointerException(); |
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62 } |
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63 if (off < 0 || len < 0 || off > b.length - len) { |
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64 throw new ArrayIndexOutOfBoundsException(); |
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65 } |
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66 adler = updateBytes(adler, b, off, len); |
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67 } |
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68 |
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69 /** |
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70 * Updates checksum with specified array of bytes. |
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71 */ |
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72 public void update(byte[] b) { |
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73 adler = updateBytes(adler, b, 0, b.length); |
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74 } |
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75 |
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76 /** |
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77 * Resets checksum to initial value. |
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78 */ |
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79 public void reset() { |
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80 adler = 1; |
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81 } |
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82 |
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83 /** |
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84 * Returns checksum value. |
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85 */ |
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86 public long getValue() { |
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87 return (long)adler & 0xffffffffL; |
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88 } |
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89 |
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90 private native static int update(int adler, int b); |
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91 private native static int updateBytes(int adler, byte[] b, int off, |
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92 int len); |
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93 } |